Being cooped up with a dysfunctional family for several days over Christmas is a nightmare many of us cannot avoid, but is probably more fun than sitting through this film.
The film has many ways to make its viewers suffer: an almost total lack of humour; a morbid insistence on medical pathology (at one point in literally microscopic detail); a great deal of smoking (but no discernible eating! I left none the wiser as to what they cooked and ate the whole time); no real narrative arc.
Visually, you're subjected to a restless round of changing characters against a background of cluttered interiors, occasionally relieved by shots of hospital corridors or unprepossessing glimpses of a very drab Roubaix. The lighting is flat, the colour often washed-out and grainy.
There's some good acting here by all concerned, but Deneuve, while having plenty of on-screen time, has little opportunity to do more than obsess about her medical prognosis. Amalric is suitably complex and volatile as Henri, but Henri's ability to be dead drunk one minute and bright-eyed (or even happily jogging) the next stretches credulity.

Catherine Deneuve is amazing of course!